This paper presents an experimental study dealing with the burning rate of pool fire in a confined and ventilated compartment within the framework of nuclear safety research. Based on full-scale pool fire experiments, it provides new information to improve understanding of burning rate mechanisms in confined and ventilated fire scenario. First of all, the paper describes the experiments conducted in both a free atmosphere and a compartment; the facility, instrumentation and fire source are detailed. Then, an analysis is made comparing free atmosphere and compartment burning rate for the same fire scenario (0.4 m2 TPH pool fire). In compartment, burning rate versus time reveals three different periods: a first period when free atmosphere and compartment burning rate are identical, a second unsteady period, during which the burning rate is higher in a compartment than in a free atmosphere and a third steady period. From video-recorder and image analysis, a detailed description of the second unsteady region shows oscillating and periodic flame behaviour resulting in significant increase of the burning rate. The effects of the ventilation rate and the pool area on this phenomenon are demonstrated. The results provide new experimental information that contribute to improving understanding of burning rate in a compartment.